Non linear filter with group delay at pre-response frequency for high res radio
AssigneeLenbrook Industries Limited
InventorsPeter Graham Craven, John Robert Stuart
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Abstract
Methods and devices are described for reducing the audible effect of pre-responses in an audio signal. The pre-responses are effectively delayed by employing a digital non-minimum-phase filter, which includes a zero lying outside the unit circle in its z-transform response. This zero is not paired with another zero at a reciprocal position inside the unit circle, as this would linearise the phase modification. The filtering can introduce a greater group delay at the pre-response frequency than at a low frequency, such as 500 Hz or even 0 Hz. The technique can be used to reduce pre-responses in an existing audio signal and also to pre-empt pre-responses that would be introduced to the audio signal by subsequent processing.
Claims30
A method for reducing the audible effect of a pre-response having energy at a pre-response frequency, the method comprising:
- receiving a digital audio signal;
- generating a modified digital audio signal by introducing group delay at the pre-response frequency by filtering the digital audio signal using a digital non-minimum-phase filter having a z-transform response that includes a zero lying outside the unit circle whose phase response is not linearised by a zero at a reciprocal position inside the unit circle;
- and
- providing the modified digital audio signal for further processing.
A method for reducing the audible effect of a pre-response having energy at a pre-response frequency, the method comprising:
- receiving a digital audio signal;
- generating a modified digital audio signal by introducing group delay at the pre-response frequency by filtering the digital audio signal using a digital non-minimum-phase filter having a z-transform response that includes a zero lying outside the unit circle, wherein the zero is selected to create a greater group delay at the pre-response frequency than at a frequency of 0 Hz;
- and
- providing the modified digital audio signal for further processing.
A non-transitory computer readable medium having stored therein instructions that when executed on a processor, cause the processor to perform a method for reducing the audible effect of a pre-response having energy at a pre-response frequency, comprising the steps of:
- receiving a digital audio signal;
- generating a modified digital audio signal by introducing a group delay at the pre-response frequency by filtering the digital audio signal using a digital non-minimum phase filter having a z-transform response that includes a zero lying outside the unit-circle whose phase response is not linearized by a zero at a reciprocal position inside the unit circle;
- and
- providing the modified digital audio signal for further processing.
Dependencies are inferred from the claim text.